According to a combustion apparatus of a background art, mainly, a gas supply path thereof and a gas supply portion on a primary side (gas infrastructure side) are connected by way of a gas pipe, a gas is supplied to the combustion apparatus, and heat by combustion is utilized for hot water supply or the like.
FIG. 7 is a block diagram showing a constitution of the combustion apparatus of the background art. As shown in FIG. 7, the combustion apparatus of the background art generally includes a combustor 101, a heat exchanger 102 of transferring heat thereof to water or the like, control parts of controlling to supply gas, combustion air, heat recovery water or the like respectively to the combustor 101 and the heat exchanger 102, and a control unit 103 of controlling the control parts.
Further, it is general that a gas cutoff valve 105 is provided on a downstream side of a portion of connecting a gas pipe and a gas supply path 104 of the combustion apparatus, and the combustion apparatus is constituted such that a total thereof including the gas cutoff valve 105, the combustor 101 and the heat exchanger 102 and the like is covered by a cabinet 100 constituted by a metal or the like. That is, the gas cutoff valve 105 is arranged at the inside of the cabinet 100 along with the combustor and the heat exchanger 102 and the like (refer to, for example, JP-A-4-292744).
As a measure against gas leakage of the combustion apparatus, there is adopted a constitution in which a gas leakage detection unit 107 is installed at the inside of the combustion apparatus, and gas leakage is prevented by cutting off the gas cutoff valve by the control unit 103 of the combustion apparatus by a detect signal detecting the gas leakage.